Archive for the ‘PCB News’ Category

5 Tips Tell You How to Solder BGA Better in PCBA

Monday, May 29th, 2023

BGA (Ball Grid Array) soldering is a widely used method in the electronics manufacturing industry for mounting integrated circuits onto printed circuit boards (PCBs). This method provides a more compact and reliable connection compared to traditional through-hole or surface mount technology (SMT). However, the complexity of BGA soldering poses various obstacles during the manufacturing process. Herein, we will explore the challenges faced in BGA soldering and discuss effective strategies to address them.

What is BGA Soldering?

BGA soldering is a technique that involves the attachment of integrated circuit packages to a PCB using an array of solder balls. These solder balls are typically made of lead-based or lead-free alloys, depending on environmental regulations and specific requirements. The BGA package consists of a substrate, which acts as a carrier for the integrated circuit, and the solder balls that form the electrical and mechanical connections between the package and the PCB.

(BGA_balls)

The Importance of BGA Soldering in Electronics Manufacturing

BGA soldering plays a critical role in the manufacturing of various electronic devices such as computers, smartphones, and gaming consoles. The increased demand for smaller and more powerful electronics has driven the adoption of BGA packages. Their compact size and high pin density make them suitable for advanced applications where space is limited.

Challenges Faced in BGA Soldering

  • Component Alignment and Placement

One of the primary challenges in BGA soldering is ensuring accurate component alignment and placement on the PCB. The small size of the solder balls and the dense layout of the BGA package make it difficult to achieve precise positioning. Misalignment during the assembly process can result in solder bridges, open connections, or mechanical stress on the package.

To address this challenge, manufacturers employ advanced technologies such as Automated Optical Inspection (AOI) and X-ray Inspection. AOI systems use cameras and image processing algorithms to verify the correct alignment and placement of BGA components. X-ray inspection, on the other hand, allows manufacturers to see beneath the surface of the PCB and detect any misalignment or defects that may not be visible to the naked eye.

(Alignment)
  • Solder Paste Application

Another significant challenge in BGA soldering is achieving precise and consistent solder paste application. Solder paste, a mixture of solder alloy and flux, is applied to the PCB pads before placing the BGA package. Inadequate or excessive solder paste can lead to solder defects such as insufficient solder joints, solder voids, or solder bridging.

To overcome this challenge, careful attention must be given to stencil design and aperture selection. Stencils with appropriate thickness and properly sized apertures ensure accurate solder paste deposition. Additionally, manufacturers can employ Solder Paste Inspection (SPI) systems to verify the quality and consistency of the solder paste applied. The solder paste that Best Technology uses is SAC305 solder paste.

(SAC305_Solder_paste)
  • Temperature Profiling

Temperature profiling, or we can say the thermal management, it is crucial in BGA soldering to ensure proper reflow of the solder paste. The reflow process involves subjecting the PCB to a carefully controlled temperature profile, allowing the solder paste to melt, form a reliable joint, and solidify. Inadequate temperature profiling can lead to insufficient solder wetting, incomplete reflow, or thermal damage to components.

Manufacturers must optimize the reflow oven setup and calibration to achieve the correct temperature profile. Thermal profiling techniques, such as the use of thermocouples and data loggers, help monitor and control the temperature during the reflow process.

  • Reflow Process

The reflow process itself presents challenges in BGA soldering. The soak zone, ramp rates, and peak temperature must be carefully controlled to prevent thermal stress on the components and ensure proper solder reflow. Inadequate temperature control or improper ramp rates can result in solder defects such as tombstoning, component warpage, or voids in the solder joints.

Manufacturers need to consider the specific requirements of the BGA package and follow recommended reflow profiles provided by component suppliers. Proper cooling after reflow is also essential to prevent thermal shock and ensure the stability of the solder joints.

(BGA_reflow)
  • Inspection and Quality Control

Inspection and quality control are critical aspects of BGA soldering to ensure the reliability and performance of the solder joints. Automated Optical Inspection (AOI) systems and X-ray inspection are commonly used to detect defects such as misalignment, insufficient solder wetting, solder bridging, or voids in the solder joints.

(AOI)

In addition to visual inspection techniques, some manufacturers may perform cross-section analysis, where a sample solder joint is cut and examined under a microscope. This analysis provides valuable information about the quality of the solder joint, such as solder wetting, void formation, or the presence of intermetallic compounds.

In a word, BGA soldering presents unique challenges in electronics manufacturing, primarily related to various factors. By addressing these challenges effectively, manufacturers can ensure the reliability and performance of BGA solder joints, contributing to the production of high-quality electronic devices. Best Technology has rich experience in PCBA assembly and we mounted thousands PCBs for our customers, whatever it is simple design or complex design, all the products are assemble perfect and work well in customer side. Please feel free to contact us for any questions about PCBA.

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5 PCB Testing details to make your PCB no more quality issues

Monday, April 24th, 2023

As we all know, it is very important to get a well-functional PCB from the PCB manufacturers.  A well functional PCB means that the electricity testing has been performed well at the PCB manufacturer end. However, you may have found some PCB you purchased are with some electricity issues like short & open circuits, or some visual issues like solder pad missing., etc.

Do you know how this issue come while the PCB testing process?

According to the feedback come from the customers, here we summarized some improper ways during the PCB Electricity testing process which may lead to the PCB fail to the test.

Here are some major points for your reference:

  • Incorrect direction when placing PCB board on testing worktop, the force on probes will cause indentation on boards.
  • PCB manufacturers don’t regularly maintain their testing jig, causing some malfunctions on testing jig can’t be found in time. Take the counter for example, if we do not find the counter’s fixing screw loose in time, it will cause the counter to fail to read the caliper scale. Of course, it also could be the counter is dysfunctional sometimes.
  • PCB manufacturers don’t regularly check/change the testing probes. Dirt on the testing probe cause testing results is inaccurate.
  • PCB testing operator don’t distinguish functional board from NG board due to unclear placement area.

So, if the circuit boards testing work under above improper way, do you know what effects will be on your products?

Base on some lessons learned from our customers, you may get following influences caused by improper way of the PCB testing.

Increase your quality issues

The low testing accuracy will make the functional PCB mixing together with the defective PCB.  If the PCB testing defects can’t be found in time before PCB assembly, defective products will flow into the market, which will seriously increase the quality risk hidden on the end products.

Delay your Progress

After defective PCBs are found, repairing will greatly delay the progress of the project.

Increase your overall cost

The defective PCB will cost many people and time to check and follow, this will directly to increase the overall cost of the projects.

We know deeply that poor testing will bring serious consequences for customers, so with more than 16 years experiences on Printed Circuits Board fabrication, Best Technology has rich experiences on PCB electric testing managements, and following are some of our management solutions to control our PCB testing process:

1.   We execute strictly the pre-job training 3 months in advance for the testing operator, and all the testing will be operated by the professional and experienced testers.

2. Maintain or replace the test equipment every 3 months, and use a brush to clean the tester in a regular period or replace the pin cable head to make sure there is no contaminate at the test probe.

3. Add the extra tooling hole at rails for fix purpose to make sure the placement of PCB orientation is no mistake during testing process.

4. The testing workshop must be divided clearly for the qualified board and NG board, the location to keep NG board will be marked with red line.

5. The testing process must be strictly followed with our internal PCB testing standard operating procedure.

With the help from above management solutions for the PCB E-Testing during the PCB manufacturing process, the PCB we send to customers works very well, which also make sure their products can be assembled well and deliver well in the markets. For us, more and more kindly feedback regarding the functional feedback comes from our customers, here are some good feedback from customers for your reference.

If you have any questions about PCB testing or PCB manufacturing, please feel your freely to leave your message or contact us. In our next update, we will share which test methods are used in the during the PCB Assembly.

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10 Tips to Reduce the manufacturing cost of Printed Circuit Board

Thursday, March 23rd, 2023

Many times, when PCB engineer or purchaser seek for a PCB manufacturer to make circuit boards, that always think the price is too high, but don’t know where makes the price is so high and how to optimize the cost on the premise of ensuring the quality of the circuit board. Herein, we share a very useful guideline about “Ten tips to reduce the PCB manufacturing cost”, welcome to read on!

  • Substrate

Different brands of substrate have different price. For a simple example, if you require a multi-layer PCB, Tg should greater than 150o, and PP need to over 0.20mm, then use GDM will cheaper than KB or SL. But GDM is usually used for making single or double-sided PCB, it is not recommended to make multi-layer circuit board. If you need to fabricate an 8 layers of multi-layer PCB, KB Tg170 is ideal for your choice since it has good performance and relatively cost-efficient.

  • Solder mask oil

In generally, what we should consider about the solder mask (S/M) are color and brand.

For the solder mask color, the most commonly used are green, white and black, if you would like to choose other special colors such as blue, yellow, gray, the price will be a little more costly.

From the brand aspect, currently the best brand is Taiyo solder mask, because it has high viscosity, stable dielectric constant, good insulation and oxidation resistance properties, but it is more expensive than others. Other brands of solder mask oil will be relatively cheap, but the quality is not particularly stable and can’t be guaranteed. So if the circuit boards need to used on bulk products, we recommend to use Taiyo to get a stable quality.

  • Printing film

If it is a bulk order with simple design and trace width/space >= 5/5mil, almost manufacturers will use printing film to generate traces. But please remember: the larger the board size, the higher cost of film. (Generally speaking, Prototypes or small orders are use LDI exposure machine to generate the trace, but for mass production, manufacturer will priority choose film and then use LDI.)

  • Line width/space

The thinner traces, the higher manufacturing price. Because the line is thinner, the accuracy of the equipment and the quality of the chemical solution are required to be relatively high, and the yield will be relatively low, resulting in higher costs. Each manufacturer has its capability, so choose a suitable supplier is most important, view Best’s website to check our capability.

  • Drill holes

The smaller the hole, the higher the price, the diameter of less than 0.3mm will increase the price. The more holes there are, the higher the price will be. Other special holes will also increase the cost, such as half holes, blind holes, PTH holes larger than 6.0mm, etc. Because the hole is small, only one board can be drilled at a time when drilling the hole on PCB material, which is low efficiency and the possibility of drilling a broken drill bitter is also large, resulting in higher cost.

  • Finished copper thickness

Finished copper thickness ≥2oz, and hole copper >25μm board will increase the cost. Because the price of copper itself is relatively expensive, the thicker the copper, the higher the price, coupled with the cost of additional electric copper, leads to the overall price rise.

  • Finished board thickness

There is little difference in the price of PCB with board thickness of 1.2mm and 1.6mm, but if the board thickness is 2.0mm or even thicker, its cost will increase correspondingly. The thicker the board, the more sheets of fiberglass, so the cost will increase accordingly.

  • Outline

If there are more slots, and the slots are less than 1.0mm, the cost will increase. This is because the gong groove of the board is more shaped, resulting in the processing time is elongated. In addition, if the width of the groove is small, processing can not be too fast, easy to break the milling cutter, so the processing efficiency is low, the natural production cost increases.

  • Surface treatment

Our common surface treatment processes are: OSP(antioxidant), lead HASL, lead-free HASL (environmental protection), gold plating, immersion gold, ENEPIG and some combination processes. The price of the above process is more expensive in turns, that is, OSP (antioxidant) < lead HASL < lead free HASL < gold plating < immersion gold < ENEPIG.

  • Tooling fee and testing fee

Tooling fee: in generally most of manufacturers use milling cutter to punch outline if this is a prototype order or small order. But if bulk order, it is needed to use a tooling jig, so there is a tooling fee need to pay.

Testing fee: flying probe tester is usually for small order, mass production need to use testing jig, and there is a different testing fee for both.

Above elements can affect the cost of making a board, you can try to follow those guidelines if you have a limited budget. Or if you want to know a exactly cost, please send RFQ to Best Technology, our sales will give you a best price.

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Why Consider Even-Number Multi-Layer PCBs For Your Project?

Tuesday, March 7th, 2023

With the great demands about high-tech electronic equipment, although the single sided PCB or double-sided printed circuit boards have their advantages, multi-layer designs are more beneficial for some applications, that’s why the more and more popular and wide usage of multi-layer PCBs.

(Multilayer_PCB)

Currently in the market and electronic industry, almost of the multi-layer PCB have an even number of layers such as 8, 10 or 12 layers, why designers didn’t consider an odd-number layers? Today let’s explore the reasons together.

  • Higher cost spent

Normally the standard layers of a multi-layer PCB in the industry are even-numbers, and as the manufacturing technology becomes more and more mature, the cost of fabricating a multi-layer PCB is relative competitive.

But if you want to produce odd-numbers PCB, may the odd-number layers save the cost of material for one layer but the processing cost increase significantly to an even-numbers. Because the core structure requirement for odd layered PCB increases the production cost greatly. However, an even layered PCB can save these costs and reduce the overall manufacturing cost, so why not consider the even number layers?

  • Long lead time

Long delivery time is unescapable because of the immature fabricating technology. In particular with the odd-layer, the stack up will be unbalance. For example, if it’s an odd layered circuitry, due to the standard symmetrical requirement, the layers will be separated to 2 layers in a one side and another side is 3 layers, so one of the copper layers will be etched away and the odd layered PCB may create uneven weight during the copper plating stage and result in irregular plating issues. This non-standard, odd-layered stack requires an extra core process for layer bonding and adds to the manufacturing time and cost. So, it’s always recommended to use an even number of layers in the PCB stack-up.

  • Potential quality issue

Quality is very important and crucial for end-application, and the best reason of why not design an odd-number multi-layer PCB is the odd-number layers PCB is very easy to get twist due to the unbalance copper layers. When the PCB is cooled after the multi-layer circuit bonding process, the different lamination tension between the core structure and the foil structure can cause the PCB to bend when cooled. As the board thickness increases, the risk of bending becomes greater for composite PCBs with two different structures.  The key to eliminate circuit board bending is to use balanced layering.  Although PCBs with a certain degree of bending meet the specification requirements, subsequent processing efficiency will be reduced, resulting in increased costs. Because assembly requires special equipment and technology, the accuracy of component placement is reduced, so the quality will be damaged.

In addition, the twist of an even-number layers PCB can be controlled below 0.7% (IPC 600 standard), but odd layers unable to reach to this quality standard. What’s more, when the warpage of a circuit board greater than 0.7% will seriously affect the operation of Surface Mounted Technology (SMT) process and the reliability of the whole product. Therefore, the designers do not design odd layer generally, even if the odd layer enables to achieve the function, will be designed into false even layer, that is, 5 layers designed into 6 layers, 7 layers designed into 8 layers of board.

Anyway, more layers it is, more complex & difficult the manufacturing will be, and more expensive the cost will be, and the lead time of multi-layer PCB also is different from normal one. So you must choose a right supplier who can provide One-stop service include designing, evaluating, manufacturing or even repairing. Best Technology is an expert in the production of multi-layer PCBs for many companies around the world for over 16 years. Contact us right now and send us inquiries, we are so confident that we can be one of your most reliable suppliers in China.

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“TEN Q & A” about Ceramic Printed Circuit Board

Monday, February 27th, 2023

Q1: What do the abbreviations DBC and AMB stand for?

A: DBC means “Direct Bond Copper” while full name of AMB is “Active Metal Brazed”. Both abbreviations refer to bonding technology of attaching a relatively thick copper (generally more than 0.2mm) on the ceramic substrates. These two technologies can be used to fabricate metalized ceramic substrates.

Q2: What is the mainly difference between DBC and AMB?

A: The mainly difference is AMB need to braze the copper to a ceramic board by active metal while DBC can directly connect the copper and substrate without any additional materials.

Q3: Which kind of ceramics are suitable for DBC and AMB?

A: DBC technology is suitable for oxide ceramics such as Al2O3 and ZTA. Non-oxide ceramics must be oxidized before they can be bonded to copper by DBC technology. ALN can be made into DBC or AMB ceramics, but Si3N4 only can be used as AMB substrates.

Q4: What is the function of metalized ceramic PCB?

The metallized ceramic substrate needs to carrier and interconnect multiple power semiconductor devices. The resulting electronic components are called power modules or multi-chip packages, most commonly LED packages or semiconductor packages. 

Q5: Does AMB can be used with oxide ceramics?

A: Yes, but the effective of DBC technology is better and the cost is relatively lower.

Q6: What is the most important performance need to be considered when design a new ceramic PCB?

A: It depends on the end application of product will be used in. Ceramics are chemically inert substances that are resistant to corrosion, moisture, and high temperatures, making them preferable to organic dielectrics that degrade in corrosive environments. Electrical, thermal and mechanical properties are equally important in the design of a new substrate. Dielectric strength is an important factor to meet the isolation requirements, which should be set according to the standards, specifications and regulations of the target application. Low thermal conductivity is not conducive to the heat transfer between the chip and the surrounding environment. The bending strength and fracture toughness play an important role in prolonging the service life of the substrate under thermal-mechanical stress.

Q7: How to choose a suitable substrate?

A: First, the heat dissipation of power semiconductor devices should be understood. Then, based on the chip and the ambient temperature, the required substrate thermal resistance is calculated. However, the combination of copper and ceramic may not always achieve the desired thermal resistance.  For one thing, the isolation voltage determines the minimum thickness of the ceramic. On the other hand, the thickness ratio of copper to ceramic has a great effect on the reliability. Finally, the set of applicable standards will be very limited.

Q8: Are DBC and AMB substrates suitable for high voltage applications?

A: The DBC substrate is ideal for applications with operating voltages up to 1.7 kV.  For higher operating voltages, a thicker ceramic layer is required to meet the relevant isolation requirements.  Silicon nitride (ALN) is often used because its high thermal conductivity offsets the increased thickness. In addition, resistance to partial discharge is particularly important in this application. Thus, AMB is superior to DBC techniques for this purpose unless the interfacial gap between copper and ceramics can be eliminated.

Q9: Are DBC and AMB substrates copper plated only on both sides?

A: No, both of two technologies can plate copper only on one side. But this is not a standard combination of materials, however, because the resulting flatness of the substrate is critical in multiple applications.

Q10: What are the shapes of substrates?

A: The rectangle is the cheapest and most common shape to produce. Other shapes are also available, but may incur additional production costs.

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How to choose surface finish on Printed Circuit Board?

Saturday, December 17th, 2022

When finish the PCB design, we should choose a suitable surface finish to protect traces from corrosion. Nowadays, the most popular surface treatments for PCB manufacturer to use are HASL/LF HASL, OSP and ENIG.

Different surface treatment has its unique functionality and the cost also is different. This article we will show you the pros and cons of the three surface finishing which use while the PCB manufacturing process.

HASL Surface Finish

HASL (Hot Air Solder Level) can be known as tin-lead HASL and lead-free HASL, it was the mainstream surface treatment technology in the 1980s, but with the increased of “small and high density” demands in PCB, there are less and less circuit boards use the HASL technology because it will cause the defective products due to the solder point are easy to leave on the board surface during SMT process. In view of this situation, some PCB board manufacturers or designers prefer use OSP or immersion gold to ensure the good quality products as well as smooth production process.

  • Tin-lead HASL

Advantages:

1) Economical and widely available.

2) Excellent solderability.

3)Better mechanical strength & lustrousness than lead-free HSAL.

Disadvantages: it is harmful to environment and violates RoHS compliance.

  • Lead-free HASL

Advantages: low cost, good solder performance and environmental.

Disadvantages: mechanical strength & lustrousness are not good than lead HASL.

In additional, due to the poor surface flatness of HASL circuit boards, neither leaded nor lead-free HASL is not suitable for soldering fine-pitch components or plated through-holes, because it will cause the short circuits and poor welding during the assembly process.

(LF_HASL)

OSP

OSP (Organic Solderability Preservatives) also named as pre flux, the working principle is to generate a layer of organic film chemically on the copper surface to protect the surface from oxidation or vulcanization in the room environment. Meanwhile, OSP also can increase the oxidation resistance, heat shock resistance and moisture resistance of a PCB. 

OSP is equivalent to an anti-oxidation treatment, the protective thin film can be easily removed by the flux quickly under the high soldering temperature, then it makes the exposed copper surface immediately combined with the molten solder in a very short time to become a solid solder spot.

At present, the usage of OSP surface finishing process has increased significantly because it is appropriated for both low and high-end products. If your application has no surface connection functional requirements or storage life limitations, the OSP process is the most desirable surface treatment process.

(OSP_surface_treatment)

Advantage:

1)With all the advantages of bare copper soldering, expired (more than 3 months) boards can also be resurfaced, but one time is better.

2)Good for fine-pitch, BGA and smaller components.

3)Low cost and easy to rework.

4)Simple process and easy to ensure quality.

Disadvantage:

1)OSP is easily affected by acid and humidity, so must be packed with vacuum.

2)Need to do surface treatment again if storage time more than 3 months.

3)It should be used within 24 hours after unpacking.

4)OSP is an insulating layer, so the test point must be printed with solder paste to remove the original OSP layer for electrical testing.

ENIG

ENIG (Electroless Nickel/Immersion Gold) is one of a chemical nickel gold deposition method, the working principle is to generate a layer of coating by chemical REDOX reaction to get a thicker gold layer. Currently, ENIG is mainly used in the surface of the circuit board with connection functional requirements and long storage life.

Advantage:

1)Can be stored long time as well as no oxidation.

2)Good flatness surface and suitable for small solder point components.

3)Good solderability.

4)Can be used as the base material for COB wire bonding.

Disadvantage:

1)High cost than other two surface treatments.

2)Easy to exist black-pad issue during production process.

(ENIG)

As we can know from above information, each PCB surface treatment has its own merit and demerit, you can choose the one according to the effect you want to reach, as well as your cost. 

If you don’t know which is best for you, you can send inquiry to us, our professional engineering team and PCB sales will choose the suitable one for you. Welcome to contact us if you have any other questions.

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How To Make PCB Silkscreen on Automatic Silkscreen Printer

Thursday, December 8th, 2022

If you’ve ever learned a printed circuit board, you may see some silkscreen legends printed on the PCB. Silkscreen legend plays an important role in PCB production process.  Therefore, the quality of silkscreen also is significant.

(Silkscreen)

Last time we share some acknowledges about silkscreen guideline, today we will introduce how to make PCB silkscreen on the Automatic Silkscreen Printer step by step for you.

Manufacturing processes of printing silkscreen

  • Screen fix

Step 1, we need to fix the screen on the base or workbench with a fixture, and leave 3-5mm distance away from the positioning plate when put the screen.

  • Align and position

Step 2, we need to place the circuit board on the positioning plate with right-angle positioning method or stud registration method (generally use 2 positioning pieces), make it fixed and aligned, then put down the stencil frame and adjust the positioning button, so that the PCB outline is roughly overlapping with screen. Next step, perform initial align boards according to the positioning holes or outline line, then gradually adjust to the optimal position based on pads.

  • Silkscreen ink selection and fine-tune

Step 3, we need to select the silkscreen ink according to the customer requirements, put down the screen frame and poured ink into the screen frame, and then select the length of the appropriate scraper for trial printing sample, and fine-tune the positioning until accurate. 

  • Trial printing

Step 4, we will need to do trial printing the prototypes with transparent character alignment film and check to see if there is a legend deviation, if no, then we can proceed with mass production, but if not, then the positioning should be fine-tuned again, rip off the defective film and affixed with the new one then printing again, repeat trail until qualified.

(Trail_printing_inspection)
  • Screen printing (manually)

Step 5, let’s place the circuit board (which have finished surface treatment process) on a fixed position, put down the screen frame, and then hold the scraper with both hands, at an Angle of 50°- 60 ° with even force on the scraping screen surface from front to back or from back to front. The printing material is subjected to the pressure of the scraper through the printing mesh hole and printed on the circuit board. After the scraper passes through, the screen recovers by its own tension. After the scraper is finished, the screen frame is lifted, and the sealing screen printing material is scraped back.

  • Screen printing (auto printer)

Step 6, the Angle of the scraper is an external “eight” font, usually between 20-30 degrees, you can choose the printing times according to the actual needs.

(Auto_printing)

In the past, most of the factories make the screen printing manually, it is time consuming and limited to relatively short lengths of 60 yards. So, in our manufacturing line, we have imported the automatic flat-bed screen printing.

Automatic_Silkscreen_Printer

Here I would like to share some features of the PCB silkscreen printer with you:

Features of Auto-Printer

  • High speed: the automatic screen printer has its own unique frequency conversion speed regulation device, the printing speed can be adjusted from 20 to 70 times per minute auto screen printing machine.
  • Cost-effective: the auto printer has its own electronic counter, which can automatically shut down according to the pre-designed total number, saving a lot of manpower and ink material.
  • Good quality: the automatic screen printer is very accurate in point and color, because it is equipped with a multi-color printing electric eye device, which can improve the quality of printing.
  • Good adhesive: the adhesion of the screen machine is very good, and the ink layer is relatively thick, so the text legend is not easy to fade.
  • Multi-aspect: the fully automatic screen printer can not only be used alone, but also can be connected to a UV dryer, or a slitting machine, a reminder, and other auxiliary machines.

With the help of Automatic silkscreen printer, we are able to provide “faster” and more “efficient” service to our customers, warmly welcome to contact us, we are ONLINE always!

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Differences Between Solder Mask and Solder Paste in PCB

Wednesday, December 7th, 2022

When it comes to solder mask and solder paste, there are some engineers confused about their functionalities and even most of laymen thought they are the same, this is not hypothetical, it is real that happened to me. So today let’s explain differences between Solder Mask and Solder Paste for you.

Part 1: What is Solder Mask?

If you had ever seen a printed circuit board, you may see there is a layer of green ink cover on the PCB surface while some orange-yellow areas didn’t cover by ink. In PCB industry, the green ink we called Solder Mask, or abbreviated as S/M, and exposed area is copper, they were leave as GND plane or soldering pads to mount electronic components.

Solder mask is a liquid acrylic oligomer, which has variety of colors such as red, blue, green, white, black. Green is commonly used in the process of PCB manufacturing, so some professional engineers call it as green oil.

Solder_mask

Solder mask applied on the PCB designed as a protection layer to avoid oxidation, corrosion and other environmental impacts when they leave production line. In addition, solder mask between solder pads also can help to prevent forming to solder bridge when assembly.

Below are some other functions of coating a layer solder mask:

  • Prevent physical line breaking of copper trace
  • Only weld in the area that must be soldered to avoid waste of soldering
  • Reduce copper pollution to soldering groove 
  • Prevent insulation deterioration and corrosion caused by dust, moisture and other external environmental factors 
  • With high insulation, so that the high-density circuit is possible

Part 2: What is Solder Paste?

Solder Paste also known as “Solder cream”, is a most important soldering material used in surface mount technology (SMT) process. Mainly function for soldering resistors, capacitors, ICs and other electronic components onto the PCB surface to form a permanent connection.

The solder particles are a mixture of solder formed by mixing solder powder, flux and other surfactants and thixotropic. Traditionally this used to be tin and lead, but with the legislation has been introduced around the world, to only use lead free solders. These may be made from a variety of mixtures, Best Technology commonly used is SAC305 which includes 96.5% tin, 0.5% copper and 3.0% silver, some manufacturers also use 99.7% tin and 0.3% copper, whereas there are other mixtures that include other metals including tin.

Due to the role of solder paste in assembly, solder paste storage is extremely important. However, solder paste got into drying during storing became a common problem faced by most PCBA manufacturers, so How to solve solder paste dry problem is premier.

Solder_paste

Part 3: The Difference Between Solder Mask and Solder Paste

  1. Solder mask is a formal part of PCB, but solder paste ONLY for PCB assembly.
  2. Solder mask is not allowed on the solder pads while solder paste can be printed on the solder pads openings.
  3. Solder mask is used for applying solder mask ink, but solder paste is used for applying paste.
  4. Solder mask has many available colors, but paste mask visually gray.
  5. Solder mask is coating during PCB fabrication, but solder paste is printing when PCB assembly.

With over 16 years in PCB industry, Best Technology is one of the most reliable PCB and PCBA supplier in Asia, we commit to provide high quality products with excellent service before and after sales, to take care our customers wholeheartedly, and to treat customers’ business as ours. At the same time, we keep learning and continually to improve ourselves so that we can catch up the latest technology trend and provide better and better service for our customers.

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“Eight” Safety Spacings You Must Know In PCB Design

Wednesday, December 7th, 2022

There are many places in the Printed Circuit Board Design that need to consider the safety spacing, here we summarized Eight Safety Spacings in total to show you what spacing we should pay attention to when designing, they can be separated into two categories, one is Electrical-Related Safety Spacing, and another is Non-Electrical-Related Safety Spacing.

Electrical-Related Safety Spacings

  • Wire Spacing

As far as the processing capability of the mainstream PCB manufacturer is concerned, the spacing between the wires shall not be less than 0.075mm. The minimum line distance refers to line to line, line to pad space.  From a production perspective, the larger the better, and the more common wire spacing is 0.25mm by far.

  • Diameter and Width of Pad

From the processing capability of mainstream PCB manufacturers, the minimum diameter shall not less than 0.15mm if the holes on pad requires mechanically drilled. If used laser drilling, then hole diameter must greater or equal than 0.10mm. At the same time, the tolerance of hole diameters varies slightly according to different substrates. Generally, it can be controlled within 0.05mm, and the minimum width of the pad should not be less than 0.2mm.

  • Spacing between Pad to Pad

The spacing between pads must be at least 0.2mm as far as the processing capacity of mainstream PCB manufacturers concerned.

  • Copper and Edge of the Board Spacing

The spacing between electronic copper and edge of the board should be no less than 0.30mm, and it can be set spacing rule on the “Design – Rules – Board outline” page.

If it requires a larger area of copper, it is generally needs to set 0.5mm as a retraction spacing from the edge of board. In the PCB design and manufacturing industries, engineers often shrink the large area of copper coating to the edge of the board by 20mil for mechanical considerations of the finished circuit board, or to avoid the occurrence of curling or electrical short circuit caused by the exposure of copper on the edge of the board, rather than coating whole copper to the edge of the board.

There are many methods to handle such shrink problems, such as drawing a keepout layer and then set a distance between copper and the keepout. As a professional PCB manufacturer that have rich experience over 16years, there is a much easy way to set different safety spacings for copper objects. For example, the safety spacing of the whole board set as 0.25mm, then we can set copper to 0.5mm, which can achieve a shrink distance of 0.5mm, and the dead copper that may cause in some devices also can be removed as well.

Non-Electrical-Related Safety Spacing

  • Width, Height and Spacing of Legends

We can’t make any changes during the processing of text legend film, except that the line width of legend with D-CODE less than 0.22mm (8.66mil) is enlarged to 0.22mm, that is, the line width of legends L=0.22mm (8.66mil). 

The width of the whole charact legends W=1.0mm, the height of the whole legends H=1.2mm, the spacing between the legends D=0.2mm. When the text is less than the above standard, the text legends after printing will be blurred.

  • Spacing between Via to Via

The spacing between vias to vias is preferably not less than 8mil.

  • Spacing between Legend to Pad

Legends/Silkscreens are not allowed on the pads, otherwise, the covered area can’t be tinned and which will affect the assembly process finally. Generally, manufacturer requires a 8mil space to convenient for silkscreen printing, but if your PCB is small and limited in area, it is barely acceptable to leave a 4 mil safety space.

If some legends accidentally over the pads in your design, Best Technology will remove or move to another area when get your approval to ensure good tinned.

Of course, design on a case-by-case situation.  Sometimes the screen printing is deliberately close to the pad, because when the two pads are very close, the screen printing in middle can effectively prevent the short circuit of the solder connection during soldering, and this is another case.

  • Mechanical 3D height and Horizontal Spacing

When mounting the components on the PCB surface, it is necessary to consider whether there will be conflicts with other mechanical structures in horizontal direction and spatial height.  Therefore, in the PCB design, the compatibility between components, finished products and product outer house and spatial structure should be fully considered, and the safety spacing should be reserved for each target object to ensure there is no conflicts occur in space.

In summary, there are many data and key points should be pay highly attention to while in PCB designing, Best Technology manufactures varies of good quality PCBs for our customers, so please do not hesitate to contact us when you have PCB design, we can help to evaluate it freely for you.

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Differences Between Immersion Gold and Gold Plating In PCB?

Wednesday, December 7th, 2022

With more and more extensive usage of Printed Circuit Boards, the IC become more and more integrated and IC pins on PCB are also more denser (such as 0603, 0402 spec ICs), which brings a big difficulty to SMT process. In addition, the shelf life of HASL board is very short, and Gold-plated board can solve such problems perfectly, that’s why it is common and popular to use gold board in high precision and ultra-small assembly process. Nowadays, there are two kinds of gold coating method in PCB industry – Immersion gold & Gold plating. To make you a sense of them, today we will simply introduce their definition and the differences between two of them.

Part 1: What is Immersion Gold (ENIG)

Immersion Gold also named as ENIG (Electroless Nickel/Immersion Gold) is generating a layer of coating by chemical REDOX reaction, is a kind of chemical nickel gold deposit surface finish during PCB manufacturing process. We can get a thicker layer of gold, but as its weak adhesion through immersion, it is also known as Soft Gold.

Part 2: What is Gold Plating

Gold plating is an another surface treatment of depositing a thin layer of gold on PCB surface by plating, the working principle is to dissolve nickel and gold (commonly known as “gold salt”) in the chemical potion, then immerse the circuit board in the electroplating cylinder and through the current on the copper foil surface of the PCB to generate a layer of gold plating. The gold particles attached to the PCB, as strong adhesion also known as “hard gold”. Gold plating is widely use in electronic products as its characteristics of hardness, excellent abrasion resistance and not easy to be oxidized. For example, the gold finger of flash driver in our computer is hard gold.

Part 3: The differences between Immersion Gold and Gold Plating

  • In generally, the gold thickness of immersion is thicker than plating, and immersion gold is golden yellow while gold plating is yellowish white, so just from appearance, most customers prefer like immersion gold.
  • Due to the crystal structures between them are different, immersion gold is easier to operate in SMT process, and won’t cause the poor soldering issue.
  • Immersion gold is softer than plating way, so if boards required gold fingers, it is always use plate-gold as its good wear resistance properties.
  • There is only nickel gold on the solder pad, so under the conductor skin effect, the signal transmission won’t be affected in copper layer.
  • Compared with gold plating, immersion gold has more denser crystal structure and is not easy to oxidation.
  • With the denser line width and space requirements, plating method is easily to cause short circuits, but since immersion gold board only has gold on solder pads, which won’t exist such issue.
  • The adhesive between solder mask and copper layer on circuit is stronger as there is only nickel gold on immersion board, so it is easier for engineers to make compensation when adjust line space.
  • Black-Pad won’t be happened to immersion board after assembly because it has good flatness than plating method.
  • Immersion gold is more economy than plating.

Best Technology is a professional PCB manufacturer with over 16 years experiences, and we have rich and mature technical to fabricate immersion gold and gold-plated boards. Warm welcome to contact us at sales@bestpcbs.com if you have any questions or RFQs about printed circuits, we are always online.

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